Students were reunited with their families after evacuating the school

A gunman and one of the teenage girls he was holding hostage have died after police stormed a school in the US state of Colorado.

The violent end to the siege in the small mountain town of Bailey came after the gunman threatened to harm the two female students he was holding.

The local sheriff said the gunman had shot the hostage and then himself as police attempted to rescue the girls.

The gunman initially seized six girls, but later released four of them.

The injured girl was taken by helicopter to hospital in Denver, where she later died. The other girl was unhurt.

'Tactical solution'

Park County Sheriff Fred Wegener said police had decided to storm a second-floor classroom at Platte Canyon High School, where the two girls were being held, after the gunman broke off negotiations.

He said the breakdown in communication came 30 minutes before a deadline the gunman had set.

"It was then decided that a tactical solution needed to be done in an effort to save the two hostages that were in the room," Mr Wegener told reporters.

"Officers breached the classroom with explosives and within seconds the suspect shot at entering Swat (specialised response unit) officers, then shot one of the two female hostages, then shot himself."

Mr Wegener said the motives of the gunman - described as being between 30 and 50 years old - were unknown.

"I don't know the identity of the gunman. I don't know why he wanted to do this and hopefully the investigation will reveal who it is."

The incident began when the man entered the school around noon (1800 GMT) with a gun and a rucksack, which he claimed held an explosive device, police said.

A newspaper in Park County quoted what appeared to be police radio reports.

One message described the gunman as arriving at the school with a handgun and firing a single shot when a teacher refused to do what he asked.

He then took six hostages. Negotiators later arranged the release of four of them.

Columbine massacre

Staff and pupils were evacuated from the high school and nearby Fitzsimmons Middle School while a bomb squad and Swat teams were deployed from neighbouring Jefferson County.

The two schools have nearly 800 students between them.

It was in Jefferson County in 1999 where two students killed 13 people at Columbine High School before taking their own lives.